This application is based on Application No. 2000-394725, filed in Japan on Dec. 26, 2000, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a method for manufacturing a stator having a stator core in which slots are formed at a ratio of two per phase per pole, and to an automotive alternator to which the stator is mounted.
2. Description of the Related Art
Generally, an automotive alternator includes: a stator constructed by installing a stator winding into a cylindrical stator core in which slots extending axially are formed at an even angular pitch in a circumferential direction; and a rotor having a field winding disposed on an inner circumferential side of the stator. The slots are disposed in the stator core at a ratio of one per phase per pole, in proportion to the number of phases in the stator winding and the number of magnetic poles in the rotor.
When the slots are disposed at a ratio of one per phase per pole in this manner, the amount of time that a tooth formed between the slots overlaps an adjacent pair of the magnetic poles relative to a radial direction is long, leading to increased magnetic flux leakage. This magnetic flux leakage reduces effective magnetic flux and gives rise to surges in the magnetic flux, resulting in fluctuations in the generated voltage and disturbing the output waveform, which causes ripples when the alternating current is converted into direct current.
Thus, an attempt has been proposed in Japanese Patent Laid-Open No. HEI 4-26345, for example, to reduce magnetic flux leakage by disposing the slots at a ratio of two per phase per pole to shorten the amount of time that a tooth overlaps an adjacent pair of the magnetic poles relative to the radial direction.
FIG. 18 is a schematic diagram in which part of a stator such as that described in Japanese Patent Laid-Open No. HEI 4-26345, for example, is developed into a plan.
In FIG. 18, a stator core 60 is composed by forming a magnetic steel plate into a cylindrical shape, slots 61 extending axially being disposed therein at an even angular pitch in a circumferential direction at a ratio of two per phase per pole. Here, for twelve magnetic poles in a rotor (not shown), seventy-two slots 61 are disposed in the stator core 60 so as to obtain a stator winding 63 composed of first and second three-phase alternating-current windings. The seventy-two slots 61 are disposed at a pitch corresponding to an electrical angle of 30xc2x0 from each other, being arranged in order of an a-phase slot 61a, a d-phase slot 61d, a b-phase slot 61b, an e-phase slot 61e, a c-phase slot 61c, and an f-phase slot 61f repeatedly in a circumferential direction.
An a-phase winding phase portion 63a is constructed by winding conductor wires into a wave shape in a group of the a-phase slots 61a, a b-phase winding phase portion 63b is constructed by winding conductor wires into a wave shape in a group of the b-phase slots 61b, and in addition, a c-phase winding phase portion 63c is constructed by winding conductor wires into a wave shape in a group of the c-phase slots 61c. The first three-phase alternating-current winding is constructed by forming the a-phase, b-phase, and c-phase winding phase portions 63a, 63b, and 63c wound in this manner into a Y-connection (an alternating-current connection). Here, the a-phase, b-phase, and c-phase slots 61a, 61b, and 61c into which the a-phase, b-phase, and c-phase winding phase portions 63a, 63b, and 63c are inserted have a phase difference corresponding to an electrical angle of 60xc2x0 from each other.
A d-phase winding phase portion 63d is constructed by winding conductor wires into a wave shape in a group of the d-phase slots 61d, an e-phase winding phase portion 63e is constructed by winding conductor wires into a wave shape in a group of the e-phase slots 61e, and in addition, an f-phase winding portion 63f is constructed by winding conductor wires into a wave shape in a group of the f-phase slots 61f. The second three-phase alternating-current winding is constructed by forming the d-phase, e-phase, and f-phase winding phase portions 63d, 63e, and 63f wound in this manner into a Y-connection. Here, the d-phase, e-phase, and f-phase winding phase portions 63d, 63e, and 63f have a phase difference corresponding to an electrical angle of 60xc2x0 from each other. Furthermore, the d-phase, e-phase, and f-phase winding phase portions 63d, 63e, and 63f have a phase difference corresponding to an electrical angle of 30xc2x0 from the a-phase, b-phase, and c-phase winding phase portions 63a, 63b, and 63c, respectively.
A stator is prepared by installing these six winding phase portions 63a, 63b, 63c, 63d, 63e, and 63f in the stator core 60. In an automotive alternator constructed in this manner, alternating-current outputs from the first and second three-phase alternating-current windings are each rectified by separate rectifiers, and then the rectified outputs are combined.
Thus, because the slots 61 are disposed at a ratio of two per phase per pole, portions of a tooth 62 overlapping an adjacent pair of the magnetic poles relative to the radial direction are dramatically reduced. Thus, magnetic flux leakage is reduced, enabling reductions in effective magnetic flux to be suppressed. Similarly, the generation of surges in the magnetic flux is suppressed, reducing fluctuations in the generated voltage and disturbances to the output waveform, thereby reducing ripples when the alternating current is converted into direct current.
Japanese Patent Laid-Open No. HEI 4-26345 described above does not disclose the construction of the stator winding 63 in detail, but if, for example, a stator winding is constructed using star-shaped winding units each composed by forming into a star shape an annular winding unit in which a conductor wire is wound for a predetermined number of winds, because the slots 61 are formed at a ratio of two per phase per pole, short-circuiting is more likely to occur between coil ends in coil end groups of the stator winding 63. Thus, because the alternating-current outputs from the first and second alternating-current windings constituting the stator winding 63 are combined after being rectified by separate rectifiers, short-circuiting between the first and second alternating-current windings leads to poor power generation.
Because the star-shaped winding units are installed in the stator core so as to line up in six layers radially, when a cooling airflow generated by a cooling fan is allowed to flow through the coil end groups of the stator core from an inner circumferential side to an outer circumferential side, heat dissipation from the coil ends varies according to the radial position of the coil ends. Thus, depending on the arrangement of the coil ends in the winding phase portions constituting the first and second three-phase alternating-current windings, heat generated in either of the first and second three-phase alternating-current windings may not be effectively dissipated from the coil ends, making the temperature of the stator increase excessively, thereby leading to reduced output.
One countermeasure for solving such problems has been to construct the stator winding using short U-shaped conductor segments. In that case, because coil end groups of the stator winding can be constructed such that coil ends constituted by turn portions and joint portions of free end portions of the conductor segments are disposed so as to be separated circumferentially and radially, short-circuiting is less likely to occur between the coil ends and heat dissipation from the coil ends increases. However, because the slots are formed at a ratio of two per phase per pole, the number of conductor segments used increases significantly, complicating the process of inserting the conductor segments into the slots, and the number of joints between the free end portions of the conductor segments increases significantly, making the stator production rate poor and preventing cost reductions, thereby making this an unrealistic countermeasure.
The present invention aims to solve the above problems and an object of the present invention is to provide an automotive alternator enabling the occurrence of poor power generation and decreased output to be suppressed by constructing a stator winding using star-shaped winding units from the viewpoint of improving the stator production rate and reducing costs, and installing six winding phase portions constituting two three-phase alternating-current windings into a stator core while considering the balance of radial positions of coil ends, and to provide a method for manufacturing a stator therefor.
In order to achieve the above object, according to one aspect of the present invention, there is provided an automotive alternator including:
a rotor fixed to a shaft rotatably supported by a case;
a cooling fan disposed on at least one axial end portion of the rotor;
a stator provided with:
a cylindrical stator core in which slots extending axially are formed at a ratio of two per phase per pole so as to line up circumferentially, the stator core being supported by the case so as to envelop the rotor, and
a stator winding composed of first and second three-phase alternating-current windings installed in the stator core; and
first and second rectifiers for rectifying an alternating-current output from each of the first and second three-phase alternating-current windings,
wherein the slots are arranged in order of an a-phase slot, a d-phase slot, a b-phase slot, an e-phase slot, a c-phase slot, and an f-phase slot repeatedly in a circumferential direction;
the stator winding is provided with a-phase, b-phase, c-phase, d-phase, e-phase, and f-phase winding phase portions in each of which a conductor wire coated with electrical insulation is installed in a wave shape in a slot group constituted by slots of like phase so as to extend outwards in an axial direction relative to the stator core from any given slot, extend circumferentially, and enter a subsequent slot of like phase;
the first three-phase alternating-current winding is constructed by forming the a-phase winding phase portion, the b-phase winding phase portion, and the c-phase winding phase portion into an alternating current connection;
the second three-phase alternating-current winding is constructed by forming the d-phase winding phase portion, the e-phase winding phase portion, and the f-phase winding phase portion into an alternating current connection;
the a-phase, b-phase, c-phase, d-phase, e-phase, and f-phase winding phase portions are installed in the stator core so as to line up in six layers radially and
the winding phase portions constituting the first three-phase alternating-current winding constitute three radially-outer layers and the winding phase portions constituting the second three-phase alternating-current winding constitute three radially-inner layers.
According to another aspect of the present invention, there is provided an automotive alternator including:
a rotor fixed to a shaft rotatably supported by a case;
a cooling fan disposed on at least one axial end portion of the rotor;
a stator provided with:
a cylindrical stator core in which slots extending axially are formed at a ratio of two per phase per pole so as to line up circumferentially, the stator core being supported by the case so as to envelop the rotor, and
a stator winding composed of first and second three-phase alternating-current windings installed in the stator core; and
a rectifier for rectifying an alternating-current output from the stator winding,
wherein the slots are arranged in order of an a-phase slot, a d-phase slot, a b-phase slot, an e-phase slot, a c-phase slot, and an f-phase slot repeatedly in a circumferential direction;
the stator winding is provided with a-phase, b-phase, c-phase, d-phase, e-phase, and f-phase winding phase portions in each of which a conductor wire coated with electrical insulation is installed in a wave shape in a slot group constituted by slots of like phase so as to extend outwards in an axial direction relative to the stator core from any given slot, extend circumferentially, and enter a subsequent slot of like phase;
the first three-phase alternating-current winding is constructed by forming the a-phase winding phase portion, the b-phase winding phase portion, and the c-phase winding phase portion into an alternating current connection;
the second three-phase alternating-current winding is constructed by forming the d-phase winding phase portion, the e-phase winding phase portion, and the f-phase winding phase portion into an alternating current connection;
the a-phase, b-phase, c-phase, d-phase, e-phase, and f-phase winding phase portions are installed the stator core so as to line up in six layers radially; and
a first of the winding phase portions constituting the first three-phase alternating-current winding constitutes one of three radially-inner layers and a second of the winding phase portions constituting the first three-phase alternating-current winding constitutes one of three radially-outer layers.
The winding phase portions constituting the first three-phase alternating-current winding and the winding phase portions constituting the second three-phase alternating-current winding may be lined up alternately in a radial direction.
The a-phase winding phase portion and the e-phase winding phase portion may constitute a first pair of layers on an inner circumferential side, in an intermediate portion, or on an outer circumferential side in a radial direction, the b-phase winding phase portion and the f-phase winding phase portion may constitute a second pair of layers on the inner circumferential side, in the intermediate portion, or on the outer circumferential side in the radial direction, and the c-phase winding phase portion and the d-phase winding phase portion may constitute a third pair of layers on the inner circumferential side, in the intermediate portion, or on the outer circumferential side in the radial direction.
A coil end group of the stator winding may be constituted by coil ends composed of portions of the conductor wires extending outwards from any given slot, extending circumferentially, and entering a subsequent slot of like phase, a varnish being impregnated into the coil end group.
Each of the a-phase, b-phase, c-phase, d-phase, e-phase, and f-phase winding phase portions may be constituted by a divided winding portion.
Radially-adjacent crossover portions of the coil ends may be offset axially.
According to yet another aspect of the present invention, there is provided a method for manufacturing a stator for an automotive alternator including:
an annular winding unit formation process for forming an annular winding unit by winding a continuous wire into an annular shape for a predetermined number of winds,
a star-shaped winding unit formation process for forming a star-shaped winding unit from the annular winding unit, the star-shaped winding unit being composed of slot-housed portions disposed at an even angular pitch in a circumferential direction alternately linked by linking portions on a radially-inner side and a radially-outer side; and
a winding unit installation process for installing six phases of the star-shaped winding units into a cylindrical stator core formed with slots at a ratio of two per phase per pole,
wherein the winding unit installation process is provided with:
a first winding unit installation process for installing a first set of three phases of the star-shaped winding units into the cylindrical stator core so as to be stacked and offset by a predetermined amount in a circumferential direction, and
a second winding unit installation process for installing a second set of three phases of the star-shaped winding units into the cylindrical stator core so as to be stacked and offset by the predetermined amount in the circumferential direction.
The slot-housed portions in the sets of three phases of the star-shaped winding units in the first and second winding unit installation processes may be installed in the stator core so as to be stacked and offset by two slots from each other in the circumferential direction.
According to yet another aspect of the present invention, there is provided a method for manufacturing a stator for an automotive alternator including:
an annular winding unit formation process for forming an annular winding unit by winding a continuous wire into an annular shape for a predetermined number of winds;
a star-shaped winding unit formation process for forming a star-shaped winding unit from the annular winding unit, the star-shaped winding unit being composed of slot-housed portions disposed at an even angular pitch in a circumferential direction alternately linked by linking portions on a radially-inner side and a radially-outer side; and
a winding unit installation process for installing six phases of the star-shaped winding units into a cylindrical stator core formed with slots at a ratio of two per phase per pole,
wherein the winding unit installation process is provided with:
a first winding unit installation process for installing a first set of two phases of the star-shaped winding units into the cylindrical stator core so as to be stacked and offset by a predetermined amount in a circumferential direction,
a second winding unit installation process for installing a second set of two phases of the star-shaped winding units into the cylindrical stator core so as to be stacked and offset by the predetermined amount in the circumferential direction, and
a third winding unit installation process for installing a third set of two phases of the star-shaped winding units into the cylindrical stator core so as to be stacked and offset by the predetermined amount in the circumferential direction.
The slot-housed portions in the sets of two phases of the star-shaped winding units in the first, second, and third winding unit installation processes may be installed in the stator core so as to be stacked and offset by three slots from each other in the circumferential direction.